Aircraft hoses and fuel lines are often exposed to chemicals, high heat and other environmental conditions during their lifetimes. Various aging mechanisms cause the hoses and fuel lines to degrade and then to crack and leak, or fail altogether. Some aging mechanisms include rapid changes in environmental temperatures over substantial periods of time, sustained periods of severe vibrations, and exposure to deleterious chemicals and other similar agents.
Various measures have been implemented to prevent fuel line and hose leaks and failures. For example, sections of such components have been extracted and tested in a laboratory environment. But this is counterproductive as it leads to destruction of the components and the necessity then to replace them. Another technique has been to implement maintenance schedules mandating fuel line replacement. Such schedules have been designed to ensure safe operation, especially in aircraft where the hoses and fuel lines are exposed to the harshest environments. As a result, these components in many aircraft are often needlessly replaced according to the schedules even though they still have useful life left in them. Moreover, the replacement maintenance is costly and time consuming.
It would therefore be most desirable if an apparatus and method were available to non-destructively measure the degradation that has occurred in the hoses and fuel lines so that replacement intervals could be established according to need rather than per a schedule. Such a device would drive down maintenance costs and minimize aircraft downtime.
Nondestructive testing techniques employing dielectric spectroscopy and dielectric loss as a measure of polymer aging have been developed to non-destructively inspect the mechanical properties of a polymer material structure, as has been disclosed by R. A. Pethrick, D. Hayward, B. K. McConnell, and R. L. Crane in their paper “Use of high and low frequency dielectric measurements in the NDE of adhesively bonded composite joints”, and in the document entitled “Novel non-destructive technique to assess the degradation of adhesively bonded composite structures” authored by P. Boinard R. A. Pethrick, W. M. Banks, and R. L. Crane. However, neither of these techniques have been successfully used in the non-destructive testing of tubes or hoses with polymer inner walls.
Accordingly, there is a need for a method and apparatus for nondestructively measuring the amount of deterioration and remaining useful life of polymeric parts as they experience degradation through aging and exposure to harsh heat or chemical environments. Embodiments of the disclosure are directed toward satisfying this need.